This invention relates generally to the field of medical devices and more particularly to the field of medical devices for use in infusion therapy and even more particularly to catheters and catheter introducers.
Catheters, particularly intravenous (IV) catheters, are used for directing fluid into or withdrawing fluid from a patient. The most common type of IV catheter is an over the needle peripheral IV catheter. As its name implies, an over the needle catheter is mounted over an introducer needle having a sharp distal tip. The catheter and the introducer needle are assembled so that the distal tip of the introducer needle extends beyond the distal tip of the catheter. The resulting assembly is inserted through the patient""s skin into a peripheral blood vessel, i.e. a smaller blood vessel that is not connected directly to the heart but is one of the branches of the central blood vessels that are directly connected to the heart. Once placement of the assembly in the blood vessel is verified by flashback of blood in the needle and in a flashback chamber located at the proximal end of the needle, the needle is withdrawn leaving the catheter in place. Peripheral IV catheters tend to be relatively short, and are on the order of about one and one-half inches in length. Such catheters are used to infuse fluid such as normal saline solution, various medicaments and total parenteral nutrition to treat the patient in whom the catheter is placed.
Another type of IV catheter is a peripherally inserted central catheter (PICC). This catheter is substantially longer than a standard peripheral IV catheter. It is placed in a peripheral blood vessel but is advanced through the vasculature so that typically the distal tip of the catheter is in one of the central blood vessels such as the superior vena cava and is adjacent to the heart. PICCs are typically used for extended infusion therapy protocols. In order to place a PICC into a patient, a catheter introducer is used because a typical PICC does not have sufficient column strength to be inserted into a blood vessel in the same way that a standard peripheral IV catheter is placed in a blood vessel.
A catheter introducer is a polymeric tubular member having a hub at its proximal end to facilitate manipulation of the device. The catheter introducer is used with an introducer needle in much the same manner that a standard over the needle peripheral IV catheter is used with an introducer needle. Thus the catheter introducer is located coaxially over the introducer needle with the distal end of the introducer needle extending distally beyond the distal end of the catheter introducer. The catheter introducer and introducer needle assembly is placed into a peripheral blood vessel in much the same manner that a standard over the needle peripheral IV catheter is placed into a patient""s blood vessel. When the catheter introducer and introducer needle assembly is properly located in the appropriate blood vessel, the introducer needle is removed from the catheter introducer. A PICC is then inserted through the catheter introducer and advanced through the vasculature into its proper location. Alternatively, a guidewire may be inserted through the catheter introducer first so that when the PICC is inserted over the guidewire and through the catheter introducer, the guidewire acts as a track for the PICC to facilitate proper placement of the PICC. Once the PICC is properly placed in the vasculature, the catheter introducer is removed from the patient leaving only the PICC behind.
In order to remove the catheter introducer from the patient with a PICC inserted therethrough, the catheter introducer must be split into two pieces in order for it to be removed from the patient. The catheter introducer cannot be simply withdrawn proximally over the PICC because the PICC typically has a proximal hub or other configuration adjacent to its proximal end that is larger than the internal diameter of the catheter introducer. Thus when the distal end of the PICC is inserted into the patient through the catheter introducer, the proximal hub on the catheter introducer blocks the proximal withdrawal of the catheter introducer from the PICC. The solution to this problem is to have the body of the catheter introducer formed with two longitudinal extending preferential tear lines that are generally about 180 degrees apart or at least substantially displaced from one another to allow the catheter introducer to be split into two pieces. Such tear lines facilitate splitting of the catheter introducer. These preferential tear lines are generally formed by skiving, i.e. cutting the preferential tear lines into the exterior of the tubular body of the catheter introducer by a knife or some sharp blade. Such a process typically works for its intended purpose but manufacturing problems do exist.
The distal portion of the catheter introducer is preferably formed with a taper having a particular configuration. Such a taper is typically used for standard peripheral over the needle IV catheters and is disclosed in U.S. Pat. No. 4,588,398. This configuration facilitates insertion of the catheter or the catheter introducer into the patient and minimizes peel back or other deformation along the distal portion of the catheter or catheter introducer that could result in patient discomfort. Various processes can be used to form such a tapered distal portion. However, a particularly preferred process is disclosed in U.S. Pat. No. 4,661,300. This process involves the following steps: placing a blank, i.e. a tube that will be used as the catheter or catheter introducer, onto a mandrel, heating at least the distal tip of the blank, engaging the mandrel with a die having the shape desired for the distal portion of the catheter or catheter introducer, removing the die from engagement with the mandrel and removing the tipped blank from the mandrel.
Although this process forms the desired tapered distal portion on the catheter introducer, the process melts, and thus eliminates, the skive on the blank at least along the distal portion of the catheter introducer. This results in a catheter introducer having no preferential tear line along its distal portion. Thus the catheter introducer cannot be easily split making it difficult for the clinician to remove the catheter introducer from the patient during the PICC insertion procedure.
It is therefore an object of the invention to provide a splittable tubular medical device.
It is another object of the invention to provide a splittable tubular medical device that has at least one longitudinally extending preferential tear line that extends along the distal portion of the device.
It is yet another object of the invention to provide a process for manufacturing a splittable medical device that allows at least one preferential tear line to be formed in and to remain in the distal portion of the medical device even where the distal portion of the medical device is heated to form a tapered distal portion.
The splittable medical device of this invention includes a main body portion in the form of a tube. The tube includes at least one and preferably a plurality of longitudinally extending preferential tear lines. One set of preferential tear lines is located along the exterior surface of the proximal portion of the tube. This set includes two such preferential tear lines located on substantially opposite sides of the tube. A second set of preferential tear lines is located along the interior surface of the distal portion of the tube. This set includes at least two such preferential tear lines with one such preferential tear line in substantial longitudinal alignment with each preferential tear line formed along the exterior surface of the proximal portion of the tube. A hub is connected to the proximal end of the tube. The first set of preferential tear lines is properly longitudinally aligned with the hub so that when the hub is pulled apart, the force applied to the hub is transmitted to the tube along the preferential tear lines to split the tube and attached hub into two separate pieces.
The splittable medical device of this invention is formed by using a special mandrel during the tipping operation. More specifically, the splittable medical device of this invention is formned by first extruding a tube having a desired diameter and wall thickness from a suitable polymer such as polyethylene, polytetrafluoroethylene or polyurethane. Next the tube is cut to the appropriate size. The tube is then connected to a suitable hub and two longitudinally extending preferential tear lines are formed along the outer surface of the tube by drawing the sharp edge of a knife against the tube. Next, the distal portion of the splittable medical device of this invention is tipped. This is done by placing the tube over a specially designed mandrel, heating the distal end of the tube to a suitable temperature so the distal portion of the tube is flowable, advancing a die into engagement with the distal portion of the mandrel to form the desired shape along the distal portion on the tube, removing the die from contact with the mandrel and removing the tipped tube from the specially designed mandrel.
The mandrel of this invention includes a plurality of longitudinally extending ribs formed along the distal portion of the mandrel. When the distal portion of the tube is tipped using this mandrel, the internal surface of the tube is altered to include a plurality of longitudinally extending grooves along the distal portion of the tube. The grooves formed on the internal surface of the tube are complementary to the ribs on the mandrel. This configuration results in longitudinally extending internal grooves being formed along the distal portion of the tube when the distal portion of the tube is tipped using the mandrel of this invention. These grooves are preferential tear lines that are substantially longitudinally aligned with the skives, i.e. preferential tear lines, formed along the portion of the tube proximal to the internal grooved portion of the tube. Thus even though the heat used to tip the tube may melt and eliminate the skive earlier formed on the outer surface of the tube, substantially the entire length of the tube is formed with preferential tear lines which facilitate splitting of the entire length of the tube.
The above and other objects and advantages of the invention will be apparent upon consideration of the following detailed description.